Objective. To assess the impact of different health warning labels (HWL). Material and Methods. Data from the International Tobacco Control Survey (ITC Survey) were analyzed from adult smokers in Brazil, Uruguay and Mexico, each of which used a different HWL strategy (pictures of human suffering and diseased organs; abstract pictorial representations of risk; and text-only messages, respectively). Main outcomes were HWL salience and cognitive impact. Results. HWLs in Uruguay (which was the only country with a HWL on the front of the package) had higher salience than either Brazilian or Mexican packs. People at higher levels of educational attainment in Mexico were more likely to read the text-only HWLs whereas education was unassociated with salience in Brazil or Uruguay. Brazilian HWLs had greater cognitive impacts than HWLs in either Uruguay or Mexico. HWLs in Uruguay generated lower cognitive impacts than the text-only HWLs in Mexico. In Brazil, cognitive impacts were strongest among smokers with low educational attainment. Conclusions. This study suggests that HWLs have the most impact when they are prominent (i.e., front and back of the package) and include emotionally engaging imagery that illustrates negative bodily impacts or human suffering due to smoking.